Tweezers

ABSTRACT

Tweezers for holding a fragile unit including two arm members having respective free ends movable upon the application of horizontal pressure from an open position of nonvertical alignment to a closed position of vertical alignment, the arm ends include gripping surfaces for engaging and securely holding the fragile unit at its periphery when the tweezers are in a closed position.

United States Patent [191 Ploecltelmann 1111 3 741 [45] June 26, 1973TWEEZERS [76] Inventor: Sidney W. Ploeckelmann, 9 05 I SepulvedaBoulevard, Manhattan Beach, Calif. 90266 [22] Filed: Apr. 1, 1971 21Appl. No.: 130,110

[52] U.S. Cl 294/99 R, 81/43, 128/354, 294/33 [51] Int. Cl B25b 9/02[58] Field of Search 294/7, 33, 99, 3; 81/43; 128/354, 321

[56] References Cited UNITED STATES PATENTS 2,601,513 6/1952 Gladstonel28/321 3,364,933 1/1968 Leopold l28/32l Primary Examiner-Harvey C.Hornsby Assistant Examiner-Johnny D. Cherry Attorney-Harris, Kiech,Russell & Kern [57] ABSTRACT Tweezers for holding a fragile unitincluding two arm members having respective free ends movable upon theapplication of horizontal pressure from an open position of nonverticalalignment to a closed position of vertical alignment, the arm endsinclude gripping surfaces for engaging and securely holding the fragileunit at its periphery when the tweezers are in a closed position.

4 Claims, 7 Drawing Figures PATENTEOJUNZB ms 3.741.602

V II/111111111] /Nl/EN7'0R SIDNEY W PLOEC/(ELMANN y Ms ATTORNEYS HARE/5,K/Em, RUSSELL &./( e v TWEEZERS This invention relates generally totweezers and more particularly to tweezers of the type used to holdand/or manipulate fragile units such as micro-circuit wafers and thelike.

The recent development of miniature circuitry has created numerousproblems with respect to the manipulation of various fragile componentsthereof such as, for example, tiny disc-like wafers and the integratedcircuits therein. Conventional tweezers and other pincer-type tools haveproved unsatisfactory because of their damaging contact to the circuitryon the interior portion of the discs. Some tweezers have been designedto grip only the periphery of the disc to avoid such damaging contact,but even those devices are deficient, often fracturing the wafer to makeit unfit for use. Such fracturing often results from excessive pressurebeing applied through the tweezer arms to the wafer. Furthermore, suchperipheral tweezers have been awkward and inefficient because they havenot held the wafer securely and have required cumbersome hand positionsfor manual operation.

The foregoing deficiencies of the prior art have caused undue expensearising from damaged wafers and imprecise and inefficient assemblyoperations with respect to those wafers which were not damaged.Accordingly, it is a primary object of the present invention toeliminate the aforementioned deficiencies and develop new improvedtweezers specifically designed for efficient, easy, dextrousmanipulation of fragile units such as micro-circuit wafers without therisk of fracturing or otherwise damaging them.

Another primary object of the present invention is to provide tweezershaving two arm members for securely gripping such wafers at theirperiphery only, thereby eliminating any stress on the interior portionof the wafers.

A further primary object is to provide tweezers of the foregoingcharacter which apply only limited gripping pressure to the waferitself, notwithstanding any excessive force applied to the arm membersby the person operating the tweezers.

A more specific object is to provide tweezers of the foregoing characterhaving gripping areas of apprecia ble surface area on each of the armmembers for contacting the wafer and holding it therebetween, in orderto securely hold the wafer stationary and to prevent concentration ofthe gripping force at any one point on the surface of the wafer.

Another object is to provide tweezers of the foregoing character whichinclude stop means for limiting the depth of engagement of the wafer bythe arm members in order that the opposing gripping forces are appliedto the periphery of the wafer rather than the interior thereof.

Still another object is to provide tweezers of the foregoing characterwhich are actuated by application of horizontal pressure to the armmembers, and which can be operated manually without placing the hand,thumb and fingers in an awkward and cumbersome position.

A further object is to provide tweezers of the foregoing character whichhold the wafer between the arm members without having to apply anyvertical pressure to the arm members. A related object is to provide avertical distance between the two gripping surfaces of slightly lessmagnitude than the thickness of the wafer so that when the two contactsurfaces are vertically aligned with the wafer therebetween, the waferis frictionally held thereby a small spring force resulting from slightvertical flexing of the arm members.

Yet another object is to provide tweezers of the foregoing character inwhich the application of horizontal pressure to the arms moves them froman open position to a closed position to vertically align the grippingsurfaces with a portion of the periphery of the wafer therebetween.

Further objects and advantages of the invention will be evident to thoseskilled in the art from the following description of the preferredembodiment.

In the drawing:

FIG. 1 is a perspective view of tweezers incorporating a preferredembodiment of the invention, in connection with an exemplary fragileunit, such as a wafer;

FIG. 2 is a top plan view showing the arm members in open position;

FIG. 3 is a top plan view similar to FIG. 2 showing the arm members inclosed position;

FIG. 4 is a side view of FIG. 3 showing the arm member in closedposition;

FIG. 5 is a sectional view taken along line 55 in FIG. 4 showing one wayof beveling a gripping surface of an arm member;

FIG. 6 is a sectional view similar to FIG. 5 showing an alternate way ofbeveling a gripping surface; and

FIG. 7 is a sectional view similar to FIG. 5 showing another alternateway of beveling a gripping surface.

Generally speaking, the tweezers 10 include two arms 12, 14, which areconnected together, as at their ends 16, so that their respective freeends 18, 20,can be moved from the open position of FIG. 2 to the closedposition of FIG. 3. A fragile unit, such as the wafer 22, defining ahorizontal reference plane, can be securely gripped between the freeends 18, 20, of the tweezers whenever sufficient horizontal pressure isapplied to bring the free ends into substantial vertical alignment. Thestructural details of the gripping features of the free ends 18, 20, andthe structural connection of the two arms l2, 14, provide for securegripping of the wafer 22 at its periphery, while at the same timeminimizing the possibility of damage to the wafer because of excessivemanual pressure being applied to the arms of the tweezers, all of whichwill be described in detail hereinafter.

More particularly, as best shown in FIG. 1, the free end 18 of the arm12 terminates in a support member, shown as a thin rectangular plate 24,adapted to slide under a wafer 22 resting on a work table or the like.The plate 24 extends under the wafer 22 and is wide enough to provide anappreciable flat surface area on its top for contacting an underneathportion of the wafer. The free end 20 of the arm 14 terminates in asimilar but truncated rectangular plate 26 which has an appreciablesurface area on its bottom for contacting an upper portion of the wafer.When the arms 12, 14, are moved from the open position of FIG. 2 to theclosed position of FIG. 3, to vertically align the free ends 18, 20,with the wafer 22 therebetween, the contact surface of the plate 26 anda portion of the contact surface of the plate 24 frictionally engagedirectly opposite sides of a portion of the periphery of the wafer 22 tosecurely grip it, thus preventing any rotation or other movement of thewafer while the arms remain in the closed position. It will beappreciated that the resulting stress on the wafer created by theopposed gripping surfaces is spread over an appreciable area of thewafer periphery rather than being concentrated at any single point, andthereby minimizes the possibility of fracturing the wafer during theholding and/or manipulation operation.

The remainder 28 of the contact surface of the plate 24 which contacts aportion of the interior of the wafer 22 serves to further minimizedamage to the wafer by spreading the pressure created by the opposinggripping surfaces over a larger area. The absence of any opposing forceopposite the remainder 28 of the plate 24 eliminates the danger ofcircuit damage to the wafer interior which might otherwise result fromopposing gripping engagement in such interior portion. In order toprevent any such opposing gripping engagement, stop means are provided,shown in the exemplary form as a transverse ledge 30 on the arm side ofthe contacting surface of the plate 24, for abutting the edge of thefragile unit. Accordingly, the depth of engagement of the wafer by thesupport plate 24 is limited to an optimum predetermined distance.

The contact surfaces of each of the plates 24, 26, are substantiallyparallel both in the open and closed position to facilitate theeffectuation and release of the gripping engagement of the wafer 22, aswell as the gripping engagement during the manipulation operation.Furthermore, the vertical distance between both contact surfaces isintended to remain fairly constant and is designed to be slightly lessthan the vertical thickness of the wafer 22. Thus, when a wafer isplaced on the support plate 24 (FIG. 2) and the arms 12, 14, are movedto the closed position by manual application of horizontal pressurethereon (FIGS. 3, 4), the contact surface of the holding plate 26 slidesinto gripping frictional engagement with the wafer and causes similarfrictional gripping engagement to occur directly opposite on a portionof the contact surface of the support plate 24, as previously described.

It is particularly important to control the pressure upon the waferthroughout the whole operation, since excessive pressure or strain willoften fracture or otherwise damage the wafer. In this regard, thejunctions 32, 34, between the plates 24, 26, and their respective armsl2, 14, are twisted and bent so that the arms extend upwardlyapproximately forty-five degrees above the horizontal and converge atthe union of their ends 16. The junction twist is approximately ninetydegrees, such that the pincer action inherent in the tweezerconstruction is horizontal as contrasted to a vertical action whichwould result if there were no twist at the junctions 32, 34.

It will be appreciated that the structural details of the foregoingimproved connection between the arms 12, 14, allows the free ends 18,20, to slightly flex vertically to allow the wafer to fit between theopposing contact surfaces, the spring action of the arms straining toreturn to their normal position providing the necessary force tosecurely hold the wafer in position. Furthermore, only the horizontalcomponent of any manual pressure exerted on the arms l2, 14, has anysignificant effect on the free ends 18, 20, causing them to movelaterally in and out of vertical alignment, or in other words, betweenthe open and closed positions. Thus excessive manual pressures ofvarying directions and magnitudes has little or no effect on thevertical pressure exerted upon the wafer.

In order to make the initial contact and the final release of the wafer22 by the holding plate 26 smooth and easy, various types of bevels areprovided on the contact surface thereof, including an inclined planecontact surface 36 of FIG. 5, a reverse inclined plane contact surface38 of FIG. 6, and a wedge contact surface 40 of FIG. 7, each of whichprovides for damage free contact and release while also providing securegripping of an appreciable area portion of the wafer periphery.

Although an exemplary embodiment of the invention has been disclosed anddiscussed, it will be understood that other applications of theinvention are possible and that the embodiment disclosed may besubjected to various changes, modifications and substitutions withoutnecessarily departing from the spirit of the invention.

I claim as my invention:

1. Improved tweezers comprising a. a unitary device with first andsecond arm members having rearward ends joined together and terminatingat a junction allowing relative movement between said arms only in ahorizontal direction and having respective free ends adapted to hold afragile disc of predetermined thickness lying in a horizontal referenceplane;

b. said free end of said first arm member including support means forengaging an underneath portion of said fragile unit adjacent itsperiphery;

c. said free end of said second arm member including holding means forengaging an upper portion of said fragile unit adjacent its periphery;and

d. said arm members being connected to position said support means andsaid holding means in horizontal planes vertically displaced a distancesubstantially equal to said predetermined thickness of said fragiledisc, said free ends of said arms being swingable in a horizontaldirection, upon the application of manual pressure upon said arms, froma normally open position of vertical non-alignment of said support meansand said holding means to a closed position bringing said support meansand said holding means into spaced apart vertical alignment to hold saidfragile unit therebetween.

2. The improved tweezers of claim 1 wherein said support means includesa first flat gripping surface and said holding means includes a secondflat gripping surface of lesser area than said first flat grippingsurface to frictionally engage in opposing relationship said underneathportion and said upper portion, respectively, of said fragile unitadjacent its periphery to prevent rotation of the fragile unit.

3. The improved tweezers of claim 2 wherein said flat gripping surfaceof said support means is terminated on one side by a stop means forabutting an edge of the fragile unit to limit the depth of engagement ofsaid fragile unit by said support means, thereby preventing any opposingfrictional engagement of said gripping surfaces with the interiorportion of the fragile unit.

4. The improved tweezers of claim 1 wherein said first and second armmembers respectively include elongated strip means lying in a verticalplane and having spring flexibility only in a horizontal direction forcontrolling the vertical pressure upon said fragile unit by said supportmeans and said holding means even though increased pressures of diversemagnitudes and directions are applied to said arm members.

l 0 l t i

1. Improved tweezers comprising a. a unitary device with first andsecond arm members having rearward endS joined together and terminatingat a junction allowing relative movement between said arms only in ahorizontal direction and having respective free ends adapted to hold afragile disc of predetermined thickness lying in a horizontal referenceplane; b. said free end of said first arm member including support meansfor engaging an underneath portion of said fragile unit adjacent itsperiphery; c. said free end of said second arm member including holdingmeans for engaging an upper portion of said fragile unit adjacent itsperiphery; and d. said arm members being connected to position saidsupport means and said holding means in horizontal planes verticallydisplaced a distance substantially equal to said predetermined thicknessof said fragile disc, said free ends of said arms being swingable in ahorizontal direction, upon the application of manual pressure upon saidarms, from a normally open position of vertical non-alignment of saidsupport means and said holding means to a closed position bringing saidsupport means and said holding means into spaced apart verticalalignment to hold said fragile unit therebetween.
 2. The improvedtweezers of claim 1 wherein said support means includes a first flatgripping surface and said holding means includes a second flat grippingsurface of lesser area than said first flat gripping surface tofrictionally engage in opposing relationship said underneath portion andsaid upper portion, respectively, of said fragile unit adjacent itsperiphery to prevent rotation of the fragile unit.
 3. The improvedtweezers of claim 2 wherein said flat gripping surface of said supportmeans is terminated on one side by a stop means for abutting an edge ofthe fragile unit to limit the depth of engagement of said fragile unitby said support means, thereby preventing any opposing frictionalengagement of said gripping surfaces with the interior portion of thefragile unit.
 4. The improved tweezers of claim 1 wherein said first andsecond arm members respectively include elongated strip means lying in avertical plane and having spring flexibility only in a horizontaldirection for controlling the vertical pressure upon said fragile unitby said support means and said holding means even though increasedpressures of diverse magnitudes and directions are applied to said armmembers.